The proposed Program Project, entitled "Impact of Changing Health Care Markets on Vulnerable Populations and Their Providers," consists of a series of interrelated research projects that will address questions regarding the effect of health care market structure an the growth of managed care on a variety of vulnerable populations in the United States. The research plan under the program project is intended to contribute toward the fulfillment of the following long range goals: * Increase understanding of the changes and trends in health care markets and how they influence vulnerable populations and their providers. * Increase understanding of how health care market structure affects access to health insurance; access, utilization and quality of medial care; and economic and clinical outcomes form members of vulnerable populations. The Program Project will include five component projects, as well as an Administrative Core and a Data, Measures, in Synthesis Core. Each project and core will contribute to the goals and theme of the Program Project, as follows: Project 1 will assess the effects of health care market structure on the quality of care provided by hospitals, focusing on potential differential effects for safety net and on-safety net hospitals. Project 2 will assess effects of health care market structure on safety net and non-safety net hospitals with regard to participation in hospital systems and managed care networks, financial performance, service offerings, and provision of charity care. Project 3 will examine the effects of market structure on access to employer-sponsored health insurance for two vulnerable populations: workers in low wage businesses and the workers employed in rural areas. Project 4 will determine how the structure of the Medicare managed care market affects economic and clinical outcomes, including insurance choice, health status, and out-of- pocket expenses for chronically ill elderly persons. Project 5 will examine the effects of health care Data, Measures, and Synthesis Core will serve as the intellectual center for the program project,, and will provide the main locus for conceptual and methodological integration of the five component projects. In addition, the Core will create a library of contextual, market-level data on health care market structure and the safety net, and will produce reports and manuscripts that summarize and synthesize the findings of the Program Project.